The life cycle of a neutron star - David Lunney

Summary

Every century, a massive star exhausts its fuel and collapses in a supernova, forming a neutron star—a dense, spinning object with the strongest magnetic fields in the universe. These stars, born from the remnants of supernovae, are laboratories for condensed matter physics. Neutron stars can be observed as pulsars, emitting beams of radiation. They may also merge in spectacular collisions, detected by observatories like LIGO and VIRGO, providing insights into gravity waves and the origin of heavy elements.

Takeaways

• 🌌 **Supernova Birth**: A massive star's death leads to a supernova, which is a colossal explosion that seeds the galaxy with heavy elements.
• 🔮 **Neutron Star Formation**: The core of the exploded star collapses into a neutron star, an extremely dense object.
• 🧲 **Superdense Matter**: Neutron stars are so dense that they cause electrons to merge with atomic nuclei, forming neutrons.
• 🌀 **Superfluidity**: Protons and electrons within a neutron star combine to form a frictionless superfluid.
• 🌐 **Nuclear Pasta**: The neutron superfluid in the star's crust forms complex structures similar to pasta shapes under extreme pressure.
• 🌀 **Rapid Rotation**: Neutron stars spin incredibly fast due to the conservation of angular momentum from their progenitor stars.
• 🌌 **Pulsars**: Neutron stars emit beams of radiation, appearing as pulsars when observed from Earth due to their rotation.
• 📡 **Magnetic Fields**: Neutron stars possess the strongest magnetic fields known, which play a role in the formation of pulsars.
• 🌌 **Binary Systems**: Neutron stars can be part of binary systems, where they may interact with and consume a companion star.
• 🌌 **Gravitational Waves**: Collisions between neutron stars produce gravitational waves, which were first detected in 2017.
• 🔬 **Astrophysical Insights**: The study of neutron stars provides insights into the origin of heavy elements and the behavior of matter at extreme densities.

Q & A

What causes a massive star to explode in a supernova?

A massive star explodes in a supernova when it runs out of fuel after millions of years of fusing hydrogen into heavier elements, and can no longer produce sufficient energy to maintain its structure, causing it to collapse under its own gravitational pressure.

What remains after a star goes supernova?

After a supernova, what remains is a dense ball of matter called a neutron star, which is one of the densest known objects in the universe.

What is a neutron star?

A neutron star is a compact ball where protons and electrons fuse into neutrons, forming a superfluid surrounded by a crust. It is an incredibly dense object left behind after a massive star collapses in a supernova.

How dense is the material in a neutron star?

The material in a neutron star is extremely dense, equivalent to the mass of a fully-loaded container ship squeezed into the size of a human hair or the mass of Mount Everest compressed into the size of a sugar cube.

What is 'nuclear pasta' in the context of a neutron star?

'Nuclear pasta' refers to different phases of neutron superfluid deeper in the crust of a neutron star, which are squeezed into shapes resembling lasagna or spaghetti.

Why do neutron stars spin so rapidly?

Neutron stars spin rapidly because they conserve the original star's angular momentum. As the star collapses from millions of kilometers wide to just about 25 kilometers across, the spin speed increases, similar to how a figure skater spins faster when pulling in their arms.

What are pulsars, and why do they appear to blink from Earth?

Pulsars are neutron stars with strong magnetic fields that radiate beams from their magnetic poles. These beams spin like lighthouse beacons because the magnetic poles are not always aligned with the rotational axis, causing them to appear to blink when viewed from Earth.

How were neutron stars first discovered?

Neutron stars were indirectly discovered in 1967 when astrophysicist Jocelyn Bell detected a flashing signal from a pulsar.

What happens to aging neutron stars over billions of years?

Aging neutron stars slow their rotation over billions of years as they radiate away their energy in the form of electromagnetic and gravitational waves.

What is significant about neutron star collisions?

Neutron star collisions send gravitational waves through space-time, which were predicted by Einstein's theory of General Relativity. In 2017, LIGO and VIRGO observatories directly observed such a collision, which provided valuable data for understanding astrophysics and the origin of heavy elements like gold and platinum.